Centralized selection of peers as media data sources in a dispersed peer network

ABSTRACT

A multi-source peer content distribution system transfers content files from multiple, distributed peer computers to any requesting computer. The content distribution network coordinates file transfers through a mediation system including s content catalog and a host broker system. The content catalog contains an identification of each content file, the segmented subunits of each file, and the peer caches to which the subunits have been distributed. The host broker system receives content file requests issued over a network from requesting computers. In response, manifest files identifying the request corresponding content subunits and distributed cache locations are returned. The requesting computers can then retrieve and assemble the corresponding content subunits from the peer computers to obtain the requested content file.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 10/349,622, filed on Jan. 23, 2003; which is acontinuation of and claims priority to U.S. patent application Ser. No.10/132,954, filed on Apr. 26, 2002 (now abandoned), the entire contentsof each of which are expressly incorporated herein by reference.

FIELD OF THE INVENTION

The present invention is generally related to network-based contentdelivery systems and, in particular, to a streaming media contentdelivery system supporting multiple, concurrent, peer-based sources ofmultimedia content accessible subject to central mediation.

DESCRIPTION OF THE RELATED ART

The desire for high-quality, on-demand delivery of streaming multimediaand other rich digital content is a principal driving force in thecontinued development of the broadband Internet infrastructure. Indeed,with the growth of broadband connections, the number, scale, anddiversity of multimedia content servers has rapidly increased. Streamingaudio and video files, including entertainment, news broadcasts, andinstructional programming are now sourced by a variety of mainstreamInternet sites. Content delivery through streaming media is broadlyrecognized as one of the fastest growing technologies related to theInternet.

Despite the growth in interest and use, conventional content streamingsystems have not been cost-effective or particularly reliable indelivering high-quality content. Streaming media content, including inparticular high-quality audio and video, is naturally bandwidthintensive and fundamentally sensitive to varying delivery latencies.Whether due to transient transport overloads, functional interruptionsin the network infrastructure, or bandwidth limitations of a contentsource site, the result is uniformly perceived by a recipient as areduction in the quality of service of the content source site.

Because of the open and shared nature of the Internet, few practicalmechanisms can ensure the uninterrupted delivery of broadband content,typically consisting of multi-megabyte files, over the entire deliverypath from a source site to a recipient. Known schemes include the use ofnetwork edge caches distributed at strategic locations within thenetwork infrastructure controlled by an individual service provider.These network edge caches can be operated to significantly reduce thenetwork traffic through the local network space of the individualservice provider. Large edge caches are naturally required to store anysignificant amount of streaming media content. Implementing a usefulnumber of adequately scaled, geographically distributed edge cachesrequires a large capital infrastructure investment.

Quality of service issues within the domain of individual content sourcesites are relatively easier to manage. Over the past few years, highlyscaled, geographically distributed and even multiply redundant contentsource system architectures have been developed. Conventionally, thesevery large-scale systems are considered a baseline requirement to ensurea consistent high quality of service from the source sites. These sitestypically employ large-scale server farms, hosting extensive librariesof archived multimedia content, that cumulatively provide sufficientthroughput to enable real-time responsiveness and continuous on-demanddelivery. Very high-bandwidth Internet connections with sufficientcapacity to accommodate peak-demand content access requirements are alsorequired.

Unfortunately, conventional content delivery networks, including fullyscaled content server systems and extensive edge cache networks, havenot proven adequate to broadly ensure a high quality of service to allpotential users of the systems. Ultimately, any media content must bedelivered as an effectively continuous stream of multimedia data to therecipient computer. The continuity of the stream must remain within thebuffer length tolerance supported by the media player on the recipientcomputer. Transient bandwidth bottlenecks can certainly occur anywherebeyond the scope of a conventional content delivery network. Bottlenecksand delivery latencies can occur even within the network, particularlywhenever the stream data is not immediately available in a locallyaccessible edge cache. Such bottlenecks in the Internet infrastructureare unfortunately both common and unpredictable.

Transient bandwidth bottlenecks can also occur in within the contentserver system itself. The rate of content access requests is highlyvariable with unpredictable demand peaks. Whenever the access rateexceeds the capabilities of the content server system, connectionrequests, including ongoing streaming data transfers, are dropped ordelayed. Whether due to network or server bottlenecks, the resultinglatencies and gaps in the delivery of stream data packets ultimately tothe recipient are uniformly seen as source-site quality of servicefailures.

Expanding the conventional content distribution networks to preventsignificant transient bandwidth bottlenecks is generally recognized asnot practical. Due to the size and diversity of the Internet and thegrowing demands for streaming content delivery, significantly expandingthe edge cache network coverage and the capacity of all included edgecaches and streaming media source sites is simply not cost-effective.Furthermore, the costs associated with high-bandwidth Internet accessand server throughput grow proportional to peak access demands, which isdisproportionately greater than the growth of average access demands.Conventionally, a minimum of 50 percent additional access and serverbandwidth is required, if not more, to meet peak bandwidth requirements.This additional bandwidth, however, is unused typically in excess of 90percent of the time. The capital and operating cost of this additionalbandwidth is therefore not directly recoverable. Consequently, contentsites and the content delivery network operators have been severelylimited in being able to consistently and profitably deliver streamingmedia content with a high quality of service.

Consequently, there is a clear need for a content delivery networkarchitecture that can reliably provide a high quality of service tocontent stream recipients and that is cost-effective to operate.

SUMMARY OF THE INVENTION

Thus, a general purpose of the present invention is to provide anefficient peer-to-peer content distribution network system architecturecapable of efficiently providing a high quality of service in thedelivery of multimedia data streams to end-users.

This is achieved in the present invention through a multi-source peercontent distribution system transfers content files from multiple,distributed peer computers to any requesting computer. The contentdistribution network coordinates file transfers through a mediationsystem including a content catalog and a host broker system. The contentcatalog contains, directly or indirectly, an identification of eachcontent file, the segmented subunits of each file, and the peer cachesto which the subunits are distributed. The host broker system receivescontent file requests issued over a network from requesting computers.In response, manifest file identifying the request corresponding contentsubunits and distributed cache locations are located and returned to therequesting computer. The requesting computers can then retrieve andassemble the corresponding content subunits from the peer computers toobtain the requested content file.

An advantage of the present invention is that content is redundantlydistributed in the form of discrete segments throughout a peer storagenetwork, permitting retrieval of segments on a best quality-of-servicebasis determined relative to each computer system that requests astreaming media content file. Multi-source segmented delivery of contentalso distributes the transport load over multiple content sources whileensuring the availability of multiple sources for all segments. Theperceived quality-of-service is both increased and reliably maintained.

Another advantage of the present invention is that centralized mediationof segmented file transfers permits strategic planning of the ongoingsegmented file transfer load distribution. Central mediation combinedwith distributed segmented file storage enables the aggregate bandwidthof the content distribution network to be optimally utilized. Thecomplexity and cost of the central content mediation system, includingthe scale of the network access connections to accommodate worst caseusage requirements, are greatly reduced.

A further advantage of the present invention is that the mediationsystem can perform predictive seeding of the content delivery networkand adaptive modification of segment distribution in response tochanging content file demands. Historical demand patterns, peer nodeavailability and bandwidth capabilities can be used to guide thestrategic distribution of content segments throughout the contentdelivery network. Planned, periodic updates of the content distributionnetwork segment caches can be used to pre-deliver content segments tomultiple strategically selected network caches during off-hours, thusminimizing both seeding and subsequent end-user demand spikes.

Still another advantage of the present invention is that the contentdistribution network can include a multi-tiered hierarchy of contentsegment caches, including peer cache nodes, primary content distributionnodes, and seeding servers. Reliable access to content segments isensured by wide distribution of the content segments within the segmentcache storage tiers and across multiple tiers.

Yet another advantage of the present invention is that the centralmediation system can be persistently connected to and monitor the stateof the available, active peer nodes of the content distribution network.Changes in the availability and supported bandwidth of nodes within thecontent distribution network are dynamically detected and factored intothe ongoing tactical utilization of the content distribution network asmediated by the central server system.

Still another advantage of the present invention is that thedistribution of content segments is actively maintained by the mediationserver system. The distribution of content segments within the contentdelivery network, which is continuously subject to redistribution as aconsequence of content use requests, is tracked and managed by themediation server system to strategically adapt the distribution patternto optimally match demand patterns.

A yet further advantage of the present invention is that proprietarycontent is continuously protected by a combination of encryption anddigital signatures applied to the content files and to the individualcontent file segments. The mediation server system maintains theintegrity of the content file segments throughout the operations of filesegment transport, cache storage, and streaming file assembly andplayback. The integrity of content within the content distributionsystem is thus ensured by the management function of the mediationserver system.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other advantages and features of the present invention willbecome better understood upon consideration of the following detaileddescription of the invention when considered in connection with theaccompanying drawings, in which like reference numerals designate likeparts throughout the figures thereof, and wherein:

FIG. 1 is a block diagram of a content distribution network organized inaccordance with a preferred embodiment of the present invention;

FIGS. 2A and 2B provide detail views of the segmentation of a streamingmedia content file in accordance with preferred embodiments of thepresent invention;

FIG. 3 is a block diagram of a peer network client system constructed inaccordance with a preferred embodiment of the present invention;

FIG. 4 is a block diagram of a peer network mediation server systemconstructed in accordance with a preferred embodiment of the presentinvention;

FIG. 5 is a flow diagram of a streaming media content file transferexecuted with respect to a peer network client system in accordance witha preferred embodiment of the present invention; and

FIG. 6 provides a detailed flow diagram of the adaptive request processimplemented in a peer network client system constructed in accordancewith a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The content distribution network (CDN) of the present invention providesa comprehensive system solution to delivering streaming media and otherdigital content files to end-user systems with a consistent, highquality of service. The end-user systems participate in a distributednetwork of peer computer systems, organized into a tiered set of contentsources, that store and, on request, selectively forward content to anyother peer computer system within the network. The distribution ofcontent and the coordination of content requests is mediated through acentralized server system, which maintains a directory catalog of theavailable content and of the location of the content within the network.

In the preferred embodiments of the present invention, each unit ofcontent, typically represented by a content file, is segmented intodiscrete parts that are each uniquely identified in the catalogmaintained by the mediation server system. Multiple copies of eachsegment are preferably distributed to cache stores maintained throughoutthe network to ensure redundant sources of segments for any requestingpeer computer system. The distribution of segments within the network ofcaches is determined by the mediation server system. While entire setsof segments may be distributed to individual peer computer systems, themediation server system can also operate to ensure that only fragmentaryportions of content units are stored by individual peer computersystems. Through fragmentary storage, the effective security of thecorresponding content units is fundamentally increased. The redundantdistribution of segments permits transfer of the entire set of segmentsto a requesting peer with an assured high quality of service.

The mediation server system preferably manages the transfer of contentsegments within and between the various storage tiers of contentdistribution network, including content seeding peer computer systems,dedicated content distribution platforms, and end-user client nodecomputer systems. The seeding peers preferably operate as the source ofnew content segments for distribution to the content distributionnetwork and as ultimate backup sources for segments of requestedcontent. The dedicated content distribution platforms preferably operateas a middle tier for content distribution, affording a greater fan-outof the transfer load in distributing content segments to the end-userclient systems. These content distribution platforms may also be used asdedicated sources of proprietary or other content that for licensing orother reasons will not be distributed for persistent storage in theend-user tier of content caches. Finally, the end-user client node tieris typically a highly heterogenous collection of typically independentlyoperated computer systems, each used to host a segment storage cache andto participate on an ad-hoc basis in the content distribution network.Client node systems may support caches of varying size, networkconnections of varying capacity, and be available on independentschedules.

Requests for selected content units and cache content update requestsare submitted to the mediation server through preferably persistentnetwork connections. Manifest lists of the segments may be returneddirectly or indirectly through an identification of a location withinthe peer network where a copy of the manifest list is stored. Based on amanifest list, content segments are independently requested by andtransferred to nodes of the content distribution system. The peer drivensegment retrieval process is cooperatively monitored by the mediationserver and, as needed, alternate source locations for segments areprovided. Information on the performance of individual peers and thepatterns of requests are collected and evaluated on a generally dynamicbasis for the generation of request manifest lists. This information isalso utilized as a basis for the generation of cache update manifestlists, used to control the background transfer and controlling thestorage distribution of content segments throughout the network tooptimize the delivery of content in anticipation of demand.

A preferred architecture of a CDN system 10, consistent with the presentinvention, is shown in FIG. 1. The CDN system 10 preferably includes acentral server system 12 and a peer content storage network 14. Whilelogically operating as a centralized system, the various server computersystems that cooperatively function as the central server system 12 canbe remotely located, duplicated, and scaled as needed for management,performance, and commercial requirements. The operational functions ofthe central server system 12 include the preparation, includingsegmentation, of new content for publication, the distribution andmanagement of content segments throughout the peer content storagenetwork 14, monitoring the effective performance and actual contentsegment transfers between various peer nodes within the content storagenetwork 14, and responding to content and cache update requests.

In the preferred embodiments of the present invention, new content isinitially prepared through a content publisher system 16 by encoding ortranscoding a new content file or other unit of content to one ofseveral defined media content formats. The currently preferred formatsinclude the Microsoft™ WMA streaming media and the Motion PictureExperts Group MPG3 formats. Other formats can be equivalently processedand used. The content file is then encrypted through a license encodingserver. In the preferred embodiments of the present invention, aMicrosoft digital rights management (DRM) encryption system is utilizedto encrypt the content and subsequently manage the serving of licensesby a license server 20. A content unit identifier, uniquelycorresponding to the encrypted, encoded content file, and the DRMgenerated license key are provided to the license server 20.

Encrypted, encoded content files are segmented by a content segmentationserver 22. As illustrated in FIG. 2A, representing a first preferredembodiment, a content file 24 is divided into segments 26 _(1-N), eachwith a defined segment size, generally within the range of 25 kilobytesand 2 megabytes and typically on the order of 100 kilobytes. Eachsegment is then assigned the unique content unit identifier 28 and asegment sequence identifier 30, permitting a particular content file 24to be reassembled in order from a collection of the content segments 26_(1-N). The resulting construction of named segments 32 are thentransferred to a seeding peer server 34 and stored in a seeding cache 36for subsequent distribution further into the peer content storagenetwork 14. Preferably, the seeding peer server 34 is considered part ofthe peer content storage network 14.

Segment catalog records 38 _(1-N) are generated in correspondence withthe named segments 32 _(1-N). For a named segment 32 ₂, thecorresponding segment catalog record 38 ₂ includes a copy of the contentunit identifier 28 and segment sequence identifier 30 of the namedsegment 32 ₂. A security value 40, based on the data content of thesegment 26 ₂, and a field 42 permitting storage of one or more locationidentifiers are also included in the segment catalog record 38 ₂.Preferably, the security value 40 is an MD5 hash, multi-byte checksum,or other data value signature of the segment 26 ₂ sufficient tosubsequently authenticate the data integrity of the segment 26 ₂.

The location identifiers are preferably surrogate client identifiersassigned to the peer nodes within the content storage network 14. Thesesurrogate client identifiers are preferably resolvable by the centralserver system 12 to peer network storage cache addresses, preferably ina uniform resource identifier (URI) form. The current URI of a clientnode can be determined whenever the client node reconnects with thecentral server system 12. In resolving a location identifier for aclient computer system that is currently unavailable, a null URI isreturned. Preferably, location identifiers uniquely correspond to peernodes. In an alternate embodiment, where the location identifier furtheridentifies a particular cache store of named segments 32, the locationidentifier revolves to a URI identifying a node and cache combination.

The segment catalog records 38 are stored to a content catalog databasemaintained by a database server 44. As created, the location field 42 ofthe segment catalog records 38 initially contain only the locationidentifier of the seeding peer 34. Whenever a named segment 32 is copiedto or deleted from a segment cache within the storage content network14, the location field 42 the corresponding segment catalog record 38 isupdated to reflect the current set of location identifiers specifyingthe content caches from which the segment can be obtained.

In response to a content unit request, the corresponding segment catalogrecords 38 are prepared and returned as part of a content manifest. Inpreparing the content manifest, the individual segment catalog records38 are expanded by resolving the location identifiers to the completeURIs for the referenced named segments 32. The requesting peer thusreceives the necessary information to directly retrieve and validate thenamed segments 32 needed to reconstruct the requested content file 24.

A second preferred embodiment of content segmentation and cataloging isshown in FIG. 2B. As before, named segments 32 are created from thecontent file 24. Groups of segments, preferably representing contiguousportions of the content file 24 are transferred to the seeding peer 34and subsequently distributed as segment groups to content segment cacheswithin the content storage network 14.

A content manifest file 38′ is generated in combination with the namedsegments 32. The content manifest file 38′ includes the unique contentunit identifier 28, a list 30′ of the segment sequence identifiers forthe named segments 32, and the security values 40′ for each of the namedsegments 32. In the preferred embodiment of the present invention, thecontent manifest file 38′ is distributed as an implied first member ofeach segment group. Alternately, the content manifest file 38′ may bedistributed separately through the seeding peer 34 to the contentsegment caches of selected, typically high availability peer computersystems within the content storage network 14.

A series of manifest catalog records 38″_(x) are also created incombination with the named segments 32 and manifest content file 38′.Each manifest catalog record 38″_(x) is established for a respectivesegment group for the content file 24. A manifest catalog record 38″_(x)includes the unique content unit identifier 28, a list 30″ of thesegment sequence identifiers for the corresponding sequence group ofnamed segments 32, a manifest security value 40″, and one or morelocation identifiers 42″ that specify the content caches storing thecorresponding segment group of the content file 24.

The manifest security value 40″ is preferably an MD5 hash, multi-bytechecksum, or other data value signature of the content manifest file 38′sufficient to subsequently authenticate the integrity of the contentmanifest file 38′. Where the content manifest file is separatelydistributed, an additional set of one or more location identifiers areincluded with the identification identifiers 42″ to specify availablecontent segment caches that store copies of the content manifest 38′.The location identifiers 42″ as stored by the content catalog areupdated as the content manifest 38′ and segment groups are copiedbetween and deleted from content segment-caches within the contentstorage network 14.

In response to a content unit request, the manifest catalog records38″_(x) are returned to the requesting peer computer system. Thelocation identifiers 42″ are expanded URIs prior to returning themanifest catalog record 38″. The requesting peer computer system canthen obtain a copy of the manifest content file 38′ and validate thecopy against the manifest security value 40″. Individual named contentsegments 32 can then be requested from any peer computer system thatpersistently stores an encompassing segment group.

This second preferred embodiment of content segmentation and catalogingis presently preferred based on the reduced load incurred by the centralserver system 12. The content manifest file 38′, due at least to thenumber and size of included security values 40′, may be an appreciablefraction of the size of the corresponding content file 24. Distributionand retrieval of the content manifest file 38′ from the content storagenetwork 14 greatly reduces the file transfer load imposed on the centralserver system 12.

In the preferred embodiments of the present invention, the centralserver system 12 supports persistent connections established between theremotely distributed nodes of the peer content storage network 14 and apersistent network proxy server 46. The persistent connections arepreferably initiated by a client node of the peer connection storagenetwork 14 to a defined TCP/IP socket supported by the persistentnetwork proxy server 46. These persistent connections are utilized topermit peer nodes to supply the central server system 12 with a thencurrent surrogate client identifier, report status and performanceinformation from the peer connection storage network 14 to the centralserver system 12 and to request and obtain manifests.

In the absence of specific activity, as an ongoing background activity,active client nodes utilize the persistent connections to signal acontinuing availability to participate in segment data transfers withinthe peer content storage network 14. In response to activity, clientnodes also report outbound segment transfer load levels and otherperformance indicators affected by ongoing peer network participation,including any communication failures that may occur. Client nodesactively performing inbound segment data transfers from other nodes ofthe peer connection storage network 14 preferably also utilize thepersistent connections to report network data transfer rates and latencyinformation against other identified client nodes. The persistentnetwork proxy server 46 preferably collects and records this status andperformance information in a network status database maintained by thedatabase server 44. The data contained within the network statusdatabase, in effect, represents a peer network map useful to plan use ofthe peer content storage network 14.

Content unit requests, as submitted by the client nodes, are directedthrough the persistent network proxy server 46 to a host broker server48. Each content unit request provides the unique content unitidentifier for the requested content unit. A search of the contentcatalog database locates the catalog records corresponding to thecontent segments necessary to construct the requested content unit. Thereferenced locations identifiers are evaluated against the performanceinformation represented by the network peer network map to select anoptimal, redundant set of content segments. This evaluation preferablyreflects a load-balancing of the ongoing segment data transfer demandson the potentially participating nodes of the peer connection storagenetwork 14. The evaluation also considers the reported network datatransfer rates between the requesting client node or similarly situatedclient nodes and the potentially participating nodes. As a product ofthe evaluation, the host broker server 48 can produce a content recordslisting a set of content segments, collectively representing therequested content unit, that can be retrieved from specified locationswithin the peer content storage network 14. The specified locationsdetermined by the host broker server 48 thus collectively represent amediated balancing of the need to broadly distribute the system-widecontent segment transfer load across the available peer network nodesand ensure effectively uninterrupted delivery of each requested contentunit to the requesting peer nodes.

Preferably, a complete content manifest-based working specification ofthe requested content unit is dynamically constructed by a requestingclient node. The content manifest file is retrieved either from anotherclient node or through the host broker server 48. Based on the segmentcatalog records 38 _(x) or the segment group index records 38″_(x),including the content unit and segment sequence identifiers, segmentsecurity values, and the expanded location identifiers 42, 42″, theworking content manifest is constructed by the client node. Preferably,the expanded location identifiers are presented in a priority ordered bysegment sequence number and relatively preferred location from which totransfer the segment as determined by the performance and load-balancingevaluation performed by the host broker server 48.

The distribution of named content segments 32 throughout the peerconnection storage network 14 is, in the preferred embodiments of thepresent invention, actively performed by the peer nodes of the peerconnection storage network 14. Named content segments 32 are placed by acontent segmentation server 22, individually or as members of segmentgroups, in the content segment cache 36 of one or more seeding peerservers 34. The named content segments 32 are then dispatched typicallythrough the Internet 50 in response to peer node requests to variousdedicated content distribution network platforms 52, client nodeplatforms 54, 56, and potentially other seeding servers 34.

Preferably, all peer nodes within the peer connection storage network 14implement content servers, such as peer node applications 58, 60, tosupport the network transfer of named content segment 32 betweenrespective local content segment caches 36, 62, 64. The progressivedistribution, including redistribution, of named content segments 32 ispredominately effected by the peer node applications 58, 60 and anysecondary seeding peer servers 34 directly requesting sets of namedcontent segments 32 for storage in the associated content segment caches36, 62, 64. Additional distribution and redistribution of named contentsegments 32, again individually or as members of segment groups, followsfrom the on-demand transfer of the named content segments 32 of contentunits requested by individual client nodes. As named content segments 32are received by a requesting client node 54, a copy is stored at leasttransiently in the associated content segment cache 64 pending streamingto a client media player 66.

Strategic control over the distribution of the named content segments 32is preferably performed by a manifest manager server 68. In accordancewith the present invention, at least the dedicated content distributionnetwork platforms 52 and client node platforms 54, 56 periodically issuecache update manifest requests to the central server system 12 throughthe persistent connections with the network proxy server 46. Cacheupdate manifest requests are also preferably issued on each initiationof a persistent connection. A content unit request may also be treatedas a cache update manifest request.

In the preferred embodiments of the present invention, the manifestmanager server 50 determines a distribution pattern of named contentsegments 32 based on an ongoing analysis of the peer network map, a logof the recent content unit requests and segment transfers, as stored bythe broker server 48 to the database server 44, and optionallyconstraints and hints provided by central server system 12administrators. In general, the goal of the analysis is to maximize theavailability of named content segments 32 to likely requesting peernodes over network connections of sufficient, reliable bandwidth,subject to the segment cache storage size, load limitations, andreported peer node relative network connection bandwidth of individualpeer nodes. While, in a present implementation, this dynamic analysis isperformed on a progressive batch basis, a near real time evaluation andanalysis of the collected data is preferred.

Constraint information may be employed in the analysis to restrict thedistribution of the named content segments 32 of particular contentunits to defined dedicated content distribution network platforms 52, asmay be externally determined appropriate for certain types of content.Constraint information may also specify language or other meta-dataattributes of content units that can be actively considered in theanalysis to determine an appropriate distribution pattern for contentunits. Other constraint information may be provided to specify periodswithin which specific content units will be available, permittingcontrolled, progressive distribution of content segments prior to arelease date and subsequent retirement after a close date.

Hinting information is preferably provided to the manifest manager 70 toperemptorily drive the distribution of named content segments 32. Thehinting information may be specified in terms of the priority andprevalence of the distribution of named content segments 32corresponding to particular content units. The prevalence hints mayindicate desired levels of redundant copy distribution over geographicand other domains. Alternately, or in addition, the hinting informationmay be specified by associating empirical and historically-deriveddistribution patterns with specified content units. Particularly in thecase of historically-derived patterns, the distribution of previouslydistributed content units can be used as a reference for projecting thelikely demand distribution of newly released content units.

The central server system 12 preferably includes one or more web servers72, which may be geographically distributed, to provide typicallyend-user accessible interfaces for the selection of content units. Theweb servers 72 connect through network connections to the databaseserver 44 to obtain browsable and searchable lists of the content unitsavailable through the mediating operation of the central server system12. In accordance with the present invention, select web servers 72 maybe designated as the sole or limited selection source for definedcontent units. Consequently, these select web servers 72 may be operatedas the apparent source of proprietary or branded content, at least fromthe perspective of end-users, yet obtain the full use and benefit of theCDN system 10 in distributing the proprietary and branded content units.

A preferred embodiment of a peer application 60 is detailed in FIG. 3.Executed as a component of a system application on a client platform 54,a system manager 80 implements the top-level procedural logic of thepeer application 80. A network connection agent 82 provides a persistentproxy interface to the network proxy 46, supporting the bidirectionaltransfer of control messages 84, such as content unit and cachemanagement requests, and data 86, including request and cache updatemanifests. Named content segments 32 are requested and received, in apreferred embodiment of the peer application 60, through an HTTP clientcomponent 88 from remote peers. A file receiver component 90, supervisedby the system manager 80, performs the detailed transfer control of datafiles and named content segments 32 through the connection agent 82 andHTTP client 88 relative to a local content segment cache 64.

As each named content segment 32 is received, a security value isregenerated based on the data of contained segment 26 and comparedagainst a corresponding security value 40, 40′, as provided in thecurrent request or cache update manifest. A comparison failure with thesecurity value 40, 40′ indicates a corrupt named content segment 32,which is discarded. Valid named content segments 32 are stored to acontent segment cache 64 under the management control of a cache managercomponent 92 and the system manager 80. Preferably, the content segmentcache 64 is encrypted subject to a DRM license. Accesses to the namedcontent segments 32 require an encryption key acquired through a licensemanager component 94, which provides an interface 96 to a conventionalDRM client 68 and, as required through the connection agent 82, to theremote license server 20.

The peer application 60 preferably implements an HTTP server 98 toprovide conventional streaming content connectivity to an externalclient media player 66 or other streaming media content client. Astreaming content component 100 coordinates between the system manager80, for initial set-up of the content streaming session, and the cachemanager 92, for the ordered retrieval of named content segments 32corresponding to a requested content unit. Retrieved named contentsegments 32 are progressively passed by the streaming server 100 fromthe local content segment cache 64 to the HTTP server 98 for relay to amedia player 66.

The HTTP server 98 also supports named content segment 32 transferrequests from other peer nodes of the peer connection storage network14. A segment server component 102 is utilized to manage named contentsegment 32 transfers, subject to segment transfer session managementperformed by the system manager 80. The transfer of named contentsegments 32 to the HTTP server 98 is coordinated by the segment server100 with the cache manager 92 for selection of the request identifiednamed content segments 32 from the content segment cache 64.

A preferred architecture 110 of a content delivery network centralserver system 12, exclusive of segment preparation and publicationcomponents, is shown in FIG. 4. A conventional hardware-based networkconnection load balancer 112 supports a scalable set of CDN serversystems 114, 116. Each CDN server systems 114, 116 implements a set ofexecutable server components that are implemented on one or moreconventional network connected server computer systems. The CDN serversystems 114, 116 share access to a CDN database 118 configured to storeOLTP accessible data and an archive database providing storage ofrecently logged and historical data that can be used for analytic andreporting purposes.

A client proxy component 120 maintains the direct socket connections forthe persistent client sessions established against the active peer nodesof the peer connection storage network 14. A startup message is receivedby the client proxy component 120 from each peer node upon joining thepeer connection storage network 14. Completion messages are received asdifferent processes are completed by the peer nodes.

A proxy manager 122 monitors the connections established with the clientproxy component 120 to maintain a data structure representing the peernodes that are currently active and accessible. Periodic status messagesare exchanged to actively monitor the state of the connected peer nodes.Failures in the status exchange are preferably analyzed with the resultof redirecting a peer node to another CDN server system 114, 116, whichmay be able to establish a more reliable network connection, or theconnection is disconnected and the peer node is identified as inactive.

A client session component 124 establishes defined contexts forcommunications with each of the peer nodes connected to the client proxy120. Within each context, information is gathered through variousprogress, status, and logging messages received from the peer nodes. Thecollected information, as well as the activity state information managedby the proxy manager, is stored to the CDN database 118 for subsequentuse in performance analysis and activity reporting.

A host broker component 126 receives, through the client proxy 120, thepeer node content unit requests. Through OLTP database accesses, thehost broker determines an optimal set of peer nodes from which therequesting peer node can download the named content segments 32corresponding to the requested content unit. Preferably, the host brokerselects all active peer nodes that store named content segments 32,individually or in segment groups, of the requested content unit andthen orders identical copies of the named content segments 32 by theload level of the source peer node and the evaluated connection speedbetween the source and requesting peer nodes. The top segment catalogrecord 38, 38″ entries for named content segments 32 are selected andprovided in one or more request catalog messages that are then returnedto the requesting peer.

A file session component 128 actively monitors the ongoing named contentsegment 32 download and streaming operations of the individual peernodes within corresponding client sessions. In conjunction with the hostbroker component 126, a unique file session identifier is provided ineach content unit request manifest. Unique file session identifiers arealso provided in each cache update manifest. When a streaming contentunit transfer is terminated, the peer node provides a session finishedmessage to the file session component 128. A file session finishedmessage is also provided when a peer node has completed a contentsegment cache update, based on a provided cache update manifest.

A file session finished message includes the request or cache updatemanifest corresponding file session identifier and information detailingthe required transfer time, number of source peer nodes used, and otherstatistically relevant information. Network communications failures withparticular source peer nodes and other error conditions are alsoreported. The acquired information is stored to the CDN database 118 forsubsequent use in performance analysis and activity reporting.

A cache manifest manager 130 is responsible for establishing thedistribution of named content segments throughout the peer connectionstorage network 14. The collected information stored by the CDN database118 is periodically evaluated on a daily or shorter basis. Newlyavailable content units, as represented by stored segment catalogrecords 38, are considered in the evaluation. An updated distributionplan is ultimately produced and stored by the cache manifest manager 130to the CDN database 118.

A peer cache update manager 132 is responsive to cache update manifestrequests, as periodically issued by the peer nodes. Based on the segmentdistribution plan determined by the cache manifest manager 130 andpreferably further qualified by recognition of the ongoing named contentsegment 32 transfers dynamically reported to the file session component128, a cache update manifest specific to the requesting peer node isgenerated and returned.

A license manager component 134 is responsive to license requestmessages issued by client nodes in connection with content unitrequests. The request manifest, in addition to providing a requisite setof segment catalog records 38, preferably identifies the type oflicensing encryption, if any, applied to the requested content unit. Alicense request message includes the request corresponding content unitidentifier 28, a license location identifier, which specifies thelicensing authority for the requested content and requesting clientnode, and the license type identifier.

The specified license type permits the license manager 134 to validatethe requested content unit license against the typically externallicensing authority. In the preferred embodiments of the presentinvention, the license manager 134 utilizes a conventional Microsoftdigital rights manager. Where validated, a license key is generated bythe license manager 134 and provided to a license server 136. Thelicense is thus available to the client media player 66 for use indecrypting the streaming media content unit as received through theclient peer application 60. A license response message is also returnedthrough the client proxy 120 to the requesting peer node in response tothe license request message. The license response message eitheracknowledges the availability of the license key or provides avalidation failure explanation.

The preferred process 140 implemented by a client peer application 60 isshown in FIG. 5. In connection with the execution of the peerapplication 60, a client media player 66, Web browser or other clientapplication, executed on the client platform 54, permits an end-user toselect and login 142 to a chosen Web server 72. Preferably, a list ofavailable content units is displayed for selection 144 by the end-user.Based typically on an end-user selection, a content unit request isissued 146 to the CDN server system 114 currently supporting thepersistent connection to the peer application 60. The content unitrequest is brokered 148 and a request manifest 150 is returned.

Upon receipt of the request manifest, the client peer application 60determines whether an encryption license applies to the requestedcontent unit. A license validation 154 is obtained where required. Thesegment catalog records 38, 38″ provided by the request manifest areparsed and corresponding named content segment 32 transfer requests areprogressively issued 156 to the segment catalog record 38, 38″identified peer nodes. As the requested named content segments 32 arereceived 158, the integrity of each named content segment 32 is checked160. Valid named content segments are preferably at least transientlystored 162 to the content segment cache 64. An updated cache updatemanifest provided in combination with the request manifest can determinewhich named content segments 32 are to be persistently retained in thecontent segment cache 64. Named content segments 32 that fail theintegrity check are re-requested from the same or an alternate peernode.

In the preferred embodiments of the present invention, once at least theinitial named content segment 32 has been received, streaming 164 of therequested content unit is enabled to the attached client media player66. As permitted by the client media player 66, Web browser or otherclient application, a new content unit can be selected 144 at any time,terminating the current transfer, and causing a new content unit requestto be issued 146.

Periodic updates of the content segment cache 64 are scheduled by theclient peer application 60. Cache update requests are preferably issued166 automatically by the peer application 60 to the currently connectedCDN server system 114. A cache update manifest is generated 168 andreturned 170 to the requesting client peer application 60. The cacheupdate manifest is parsed by the client peer application 60 to identifyany named content segments 32, as specified by corresponding segmentcatalog records 38, that are not currently stored by the content segmentcache 64. Requests for the non-resident named content segments areissued 156 and the named content segments 32 are received 158 and stored162 to the content segment cache 64.

In an alternate embodiment of the present invention, the cache updatemanifest provides meta-information that is used by the client peerapplication 60 to qualify cache update operations. The cache updatemanifest meta-information is utilized to specify the schedule of cacheupdate requests and the location of the CDN server system 114, 116 touse as the target of the next cache update request. The meta-informationmay also be provided to specify a delay schedule for issuance of namedcontent segment 32 transfer requests. This allows the cache updatemanager 132 to fully mediate the data transfer load on the peer contentstorage network 14 both in terms of selecting the transfer source peernodes utilized and the temporal distribution of the load imposed onthose nodes. Such mediation is particularly valuable to optimallyschedule the load placed on the seeding peers 34 and dedicated CDNplatforms 52 particularly where the peer content storage network 14includes a large number of peer nodes.

The managed client peer process 180 of named content segment request andretrieval is shown in greater detail in FIG. 6. The contents of requestand cache update manifests, including meta-information, are initiallyparsed 182 upon receipt of the manifests. Deferred operations arepreferably handled through a periodic re-parsing of the manifests at thedeferred time intervals. In anticipation of the receipt of new namedcontent segments 32 beyond a client platform 54 defined cache size,named content segments 32 no longer identified in the current cacheupdate manifest are deleted 184 from the content segment cache 64.

Preferably, multiple named content segments 32 are requested 156concurrently from the peer content storage network 14. Each concurrentlyrequested named content segment 32 is also redundantly requested frommultiple peer node locations. The total number of concurrent namedcontent segment 32 transfers allowed is a dependent on the maximumacceptable load permitted on the client platform 54. Excluding theredundant transfers, a default limit is set at four concurrent transfersof unique named content segments 32. As redundant copies of namedcontent segments are received 158, the transfer bandwidths of each aremonitored. Once a reasonably stable gauge of the transfer bandwidths canbe determined, adjusted potentially for different transfer start timesand the anticipated remaining length of the named content segment 32,only the highest bandwidth transfer for each named content segment 32 ismaintained. A failure to complete any of these remaining transfers isdetected 186. A severe reduction in the transfer bandwidth is alsopreferably treated as a transfer failure. Redundant requests for thesame named content segment 32 are again reissued 188 to multiple peernode locations determinable from the manifests.

Named content segments 32 are stored 162 to the content segment cache 64as received 158. A security value for the segment data may beaccumulated as the named content segment 32 is received or computed oncethe named content segment 32 once the transfer is completed. This actualsecurity value is then compared 190 to the security value 40 provided inthe corresponding segment catalog record 38. On a comparison failure,the received named content segment 32 is deleted from the contentsegment cache 64. Redundant requests for the named content segment 32are again reissued 188.

Preferably, detailed information, including the connection latency,average bandwidth and reliability of transferring named content segments32 relative to the requesting client platform 54, is collected by theclient peer application 60. Information detailing transfer failures anddata integrity failures, along with the identity of the peer nodesparticipating in the failed transactions, is also collected. Thisperformance information is reported to the connected CDN server system114, 116, preferably in connection with the transfer completion of eachcontent unit transfer and cache update.

Thus, an efficient peer-to-peer content distribution network systemarchitecture capable of efficiently providing a high quality of servicein the delivery of multimedia data streams to end-users has beendescribed. While the present invention has been described particularlywith reference to operation over the public Internet, the presentinvention is equally applicable to the distribution over other publicand private communications networks. Additionally, the present inventionis also applicable to the rapid and efficient distribution of digitalinformation that may have use other than as streaming media content.

In view of the above description of the preferred embodiments of thepresent invention, many modifications and variations of the disclosedembodiments will be readily appreciated by those of skill in the art. Itis therefore to be understood that, within the scope of the appendedclaims, the invention may be practiced otherwise than as specificallydescribed above.

1. A system for distribution of content segments of content unitsthroughout a content delivery network, including end-usercontent-storing client peer nodes and end-user content-requesting clientpeer nodes interconnected by a wide area communications network,comprising: a) computer processing apparatus configured to analyzerequests for content to identify a distribution pattern of contentdemand between the end-user content-storing client peer nodes andend-user content-requesting client peer nodes; b) computer processingapparatus configured to determine a redundant distribution of contentsegments of a content unit among the end-user content-storing clientpeer nodes corresponding to the distribution pattern of content demand,wherein the redundant distribution is determined subject to the storageand content transfer capabilities of end-user content-storing clientpeer nodes relative to end-user content-requesting client peer nodes; c)computer processing apparatus configured to direct a copying of contentbetween end-user content-storing client peer nodes to establish apredetermined correspondence between the redundant distribution ofcontent and the distribution pattern of content demand; and d) computerprocessing apparatus configured to enable, in response to a request fora content unit from a first end-user content-requesting client peernode, transfer of a first content segment of the requested content unitfrom a first end-user content-storing client peer node and a secondcontent segment of the requested content unit from a second end-usercontent-storing client peer node.
 2. The system of claim 1 wherein thecomputer processing apparatus analysis identifies the distributionpattern as a projection of content demand based on historical demand. 3.The system of claim 2 wherein the computer processing apparatus analysisis responsive to control information selectively provided in addition tohistorical demand information to identify the distribution pattern. 4.The system of claim 3 wherein content-storing nodes are organized as aplurality of content storage tiers, wherein seed content is distributedfrom a first content storage tier, and wherein the step of directingprovides for redundant copies of the seed content to be distributed to asecond content storage tier in conformance with the predeterminedcorrespondence.
 5. The system of claim 4 wherein the computer processingapparatus analysis is responsive to control information selectivelyprovided in addition to historical demand information to identify thedistribution pattern, wherein distribution of the seed content inconformance with the distribution pattern is limited to the first andsecond content storage tiers, and wherein the computer processingapparatus enabling provides for the transient transfer of the seedcontent to the first identified node within a third content storagetier.
 6. The system of claim 3 wherein content-storing nodes areorganized as a plurality of content storage tiers including first,second and third content storage tiers, wherein first and secondpredetermined seed content are selectively distributed by a computerprocessing apparatus to the first content storage tier, whereinredundant copies of the first predetermined seed content are copied toand persistently stored within the second content storage tier, whereinredundant copies of the second predetermined seed content are copied toand persistently stored within said second and third content storagetiers, and further providing for the transient transfer of said firstand second predetermined seed content selectively from said first,second and third content storage tiers.
 7. The system of claim 6 whereinthe computer processing apparatus enabling provides for the transienttransfer of said first predetermined content exclusively from said firstand second content storage tiers.
 8. A system for distribution ofcontent segments of content units throughout a content delivery network,including content-storing end-user client peer nodes andcontent-requesting end-user client peer nodes interconnected by a widearea communications network, comprising: a) computer processingapparatus configured to deliver content segments to a plurality ofcontent-storing nodes for the storage thereof; b) computer processingapparatus configured to thereafter control a redistribution of contentsegments, including redundant content copies of segments, among theplurality of content-storing nodes; c) computer processing apparatusconfigured to monitor demand for identified content units by end-usercontent-requesting peer nodes to provide a demand history and to monitorthe content transfer performance of end-user content-storing peer nodesrelative to end-user content-requesting peer nodes to provide aperformance history; d) computer processing apparatus configured todetermine, responsive to the demand history and the performance history,a redistribution pattern for content segments, including redundantcopies of segments, within the content delivery network; e) computerprocessing apparatus configured to direct the redistribution of contentsegments, including redundant copies of segments, between end-userclient peer nodes within said network toward conformance with theredistribution pattern; and f) wherein, in response to a request for acontent unit from a first end-user content-requesting client peer node,a first content segment of the requested content unit is transferredfrom a first end-user content-storing client peer node and a secondcontent segment of the requested content unit is transferred from asecond end-user content-storing client peer node.
 9. The system of claim8 wherein the computer processing apparatus directing includes providingincremental content transfer instructions to respective end-usercontent-storing client peer nodes to obtain transfers of contentsegments between said plurality of content-storing nodes.
 10. A systemfor distribution of content segments of content units throughout acontent delivery network, including end-user content-storing client peernodes and end-user content-requesting client peer nodes interconnectedby a wide area communications network, comprising: a) means foranalyzing requests for content to identify a distribution pattern ofcontent demand between the end-user content-storing client peer nodesand end-user content-requesting client peer nodes; b) means fordetermining a redundant distribution of content segments of a contentunit among the end-user content-storing client peer nodes correspondingto the distribution pattern of content demand, wherein the redundantdistribution is determined subject to the storage and content transfercapabilities of end-user content-storing client peer nodes relative toend-user content-requesting client peer nodes; c) means for directing acopying of content between end-user content-storing client peer nodes toestablish a predetermined correspondence between the redundantdistribution of content and the distribution pattern of content demand;and d) means for enabling, in response to a request for a content unitfrom a first end-user content-requesting client peer node, transfer of afirst content segment of the requested content unit from a firstend-user content-storing client peer node and a second content segmentof the requested content unit from a second end-user content-storingclient peer node.
 11. A system for distribution of content segments ofcontent units throughout a content delivery network, includingcontent-storing end-user client peer nodes and content-requestingend-user client peer nodes interconnected by a wide area communicationsnetwork, comprising: g) means for delivering content segments to aplurality of content-storing nodes for the storage thereof; h) means forthereafter controlling a redistribution of content segments, includingredundant content copies of segments, among the plurality ofcontent-storing nodes; i) means for monitoring demand for identifiedcontent units by end-user content-requesting peer nodes to provide ademand history and to monitor the content transfer performance ofend-user content-storing peer nodes relative to end-usercontent-requesting peer nodes to provide a performance history; j) meansfor determining, responsive to the demand history and the performancehistory, a redistribution pattern for content segments, includingredundant copies of segments, within the content delivery network; k)means for directing the redistribution of content segments, includingredundant copies of segments, between end-user client peer nodes withinsaid network toward conformance with the redistribution pattern; and l)wherein, in response to a request for a content unit from a firstend-user content-requesting client peer node, a first content segment ofthe requested content unit is transferred from a first end-usercontent-storing client peer node and a second content segment of therequested content unit is transferred from a second end-usercontent-storing client peer node.